FIG. 1 is a conventional representation of a microwave window. The microwave window 1 comprises a wall 2 and typically the wall 2 comprises a ceramic material such as alumina.
The microwave window 1 furthermore comprises a core 3 passing through the wall 2, the core 3 extending in a longitudinal direction dLong.
A cladding 4 comprising a material ensuring thermomechanical and microwave matching is arranged coaxially around the wall 2.
A body 5 made of a metal, stainless steel for example, allows a coupled assembly to be created that can be assembled with an electron tube.
All of these parts are assembled by brazing, the core 3 being sufficiently small in size that expansion differences between these parts allow a satisfactory mechanical strength to be guaranteed. Typically, the diameter d1 of the core 3 is about 0.5 mm.
This first solution of FIG. 1 is complex to implement and it requires a plurality of assembly and brazing steps.
Another solution consists in using a core 3 comprising controlled expansion materials.
The low thermal expansion materials generally used are FENICO™ provided by Fenico Precision Castings of CA (or other types of expansion materials) having a low thermal elongation coefficient of about 0.0121 mm per mm at 1010° C., or molybdenum having an elongation coefficient of about 0.0057 mm per mm at 1010° C.
One drawback of microwave windows using controlled expansion materials is that these materials are highly resistive, thereby limiting power transmission capability.
Another possible solution consists in using a material such as moly-copper associating the low thermal expansion properties of molybdenum and the good energy conduction properties of copper.